Studies have been inconsistent in finding a relationship between Vitamin D and breast cancer. Now, recent research continues this ambiguity. A study published in the journal Breast Cancer Research in August 2009 found no association between postmenopausal breast cancer risk and levels of Vitamin D, regardless of hormone receptor status, body mass index, postmenopausal hormone therapy, weight gain, season of the year, or calcium intake.
However, researchers did note that:
• the source of Vitamin D might be important, with women who get the vitamin through their diet—in fortified milk or fish, for example—having higher levels circulating in their bodies. Also, dietary Vitamin D is strongly correlated with calcium, which may be effective in fighting breast cancer.
• Women living at northern latitudes—above 37° —get less Vitamin D from the sun and were more likely to have breast cancer than those in southern latitudes. This, however, could be due to chance, researchers say.
Of three previously published studies, two found a relationship between Vitamin D and breast cancer:
• An analysis of 701 cases from the Nurses' Health Study found a 27 percent lower relative risk of breast cancer in women with higher levels of Vitamin D.
• An analysis from the National Health and Nutrition Examination Survey (NHANES) reported a relative risk for fatal breast cancer among women with low levels of Vitamin D.
• Among 1005 postmenopausal cases in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial, no association was found between Vitamin D and breast cancer risk.
So, what do we make of this? My conclusion: There is no risk found in taking Vitamin D, so let's make it part of our diet. If there is a chance it helps, why not take it? Dietary sources are better than supplements. The National Institute of Health provides an overview of Vitamin D and provides a list of its sources. The best source: cod liver oil. Sure, it tastes icky, but breast cancer is no picnic either.
NOTE, this study used the terminology serum 25-hydroxyvitamin D (25(OH)D or, simplified, 25(OH)D. For clarification of this terminology, check out the Medline Plus Encyclopedia. Basically, the terms refer to the blood test that measures levels of Vitamin D in the blood. The normal range is 30 to 74 nanograms per milliliter.